Established and supported under the Australian Government’s Cooperative

FIELD EVALUATION OF THE BENEFITS OF FISH

OIL DIETARY SUPPLEMENTATION TO

MULTIPAROUS SOWS FED DURING LACTATION

AND EARLY PREGNANCY ON FERTILITY

2F-109

Report prepared for the Co-operative Research Centre for an Internationally

Competitive Pork Industry

By

Rob Smits

PO Box 78 Rivalea Australia

NSW 2646

May 2010

i

Executive Summary

The aim of this study was to assess the effect on reproductive performance of

supplementing the diet with omega 3 fatty acids from fish oil when fed to sows either

before post-weaning oestrus, during early pregnancy or continuously from lactation

through to four weeks gestation. 1216 mixed parity sows (parity 1-7) were fed one of two

lactation diets: either unsupplemented (Control lactation) and formulated using wheat,

cereals and soybean and canola meals and using tallow as the main source of fat (68 g/kg)

or the same base diet supplemented with 3 g/kg of fish oil substituting v/v with tallow

(Omega 3 lactation). Following weaning, sows continued on their treatment diet until

oestrus. Of the sows weaned and displaying oestrus, 860 sows were allocated to a 2 x 2

factorial feeding regimen and after mating, were fed either one of two gestation diets:

either unsupplemented (Control gestation) and formulated using wheat and cereals and

tallow as the main fat source (10 g/kg) or the same base diet supplemented with 6 g/kg of

fish oil substituted for tallow. Subsequent reproductive performance for weaning to

oestrus, proportion of sows re-mated, farrowing rate and subsequent litter size born live

and total born were analysed with average lifetime litter size born and lactation length as

co-variates in Univariate GLM ANOVA. There was no significant treatment effect on the

number of sows weaned, number re-mated or weaning to oestrus interval (7.0±0.2 days).

Subsequent litter size was significantly higher (P<0.05) in sows fed omega 3 supplemented

diets during lactation and through early pregnancy compared to unsupplemented Controls

(12.6 vsvs. 11.7 total born). Farrowing rates were unaffected by dietary treatment

(83.1%). Within parity analysis resulted in a larger response to supplementation detected

in mature parities (parity 4-7 weaned). In conclusion, omega 3 fatty acids from fish oil

resulted in improved subsequent litter size in older sows. Dietary supplementation offers

producers a nutritional strategy to overcome declining productivity in sows increasing in

age.

ii

Table of Contents

Executive Summary ............................................................................................................................................. i

1. Introduction ................................................................................................................................................ 1

2. Methodology ............................................................................................................................................... 2

3. Outcomes .................................................................................................................................................... 5

4. Application of Research ......................................................................................................................... 14

5. Conclusion ................................................................................................................................................. 14

6. Limitations/Risks ..................................................................................................................................... 14

7. Recommendations ................................................................................................................................... 15

8. References ................................................................................................................................................ 16

Appendices ......................................................................................................................................................... 21

Appendix 1: .................................................................................................................................................... 21

1

1. Introduction

One of the causes of high sow turnover in a breeding herd is low reproductive

performance. Over the years there have been several studies that have concluded

that reproductive failure and low fecundity contribute half of the sows culled in a

herd (Hughes and Varley, 2003). Engblom et al (2008) reported that culling for

low litter size was accentuated as parity increased in commercial herds.

Historically, the fertility of sows in commercial herds continued to increase with

age until parity 4 or 5, before declining with a productive life expectancy

averaging 8 or 9 litters (Levis, 2005, Tummaruk, et al., 2001). However, more

recent farm records show that reproductive performance is now peaking at

younger parities, before a rapid decline (Hughes and Varley, 2003, Rodriguez-Zas,

et al., 2003).

Supplementing the diets fed to sows during lactation with long-chain

polyunsaturated fatty acids (PUFA’s) from fish sources has been reported to

improve reproductive performance (Palmer, et al., 1970, Webel, et al., 2004).

Fish oil contains high levels of omega 3 eicosapentaenoic acid (EPA, C20:5) and

docosahexaenoic acid (DHA, C22:6), and dietary supplementation can increase the

tissue levels of these fatty acids in oocytes (Trujillo and Broughton, 1995,

Wakefield, et al., 2008) and embryos (Brazle, et al., 2009). PUFA’s have an

important role in regulating reproduction through the eicosanoid pathway which

synthesises prostaglandins (Caughey, et al., 2005). Altering the ratio of omega 6

to omega 3 fatty acids can alter the potency of prostaglandin activity (Innis, 2003,

James, et al., 2000), and this may be a mechanism for improved reproductive

outcomes when omega 3 sources are fed to animals (Staples, et al., 1998).

Previously we have shown that feeding a lactation diet supplemented with low

levels of fish oil (3 g/kg) increased subsequent litter size and this was

consequently related to improved embryo survival (Smits et al, unpublished,

Project 2F-102). The aim of this experiment was to investigate if there are

benefits to subsequent reproductive performance in a commercial herd when diets

are supplemented with omega 3 fatty acids from fish oil during lactation and post-

weaning, and if there are additional benefits when supplemented diets continue

to be fed in early pregnancy.

This experiment tested two hypotheses, firstly that offering sows a diet

supplemented with long-chain omega 3 fatty acids from fish oil during lactation

and post-weaning to oestrus would improve reproductive performance and

2

subsequent litter size. Secondly, fertility is enhanced when supplementation with

dietary omega-3 fatty acids is continued after mating during the period of embryo

implantation in early gestation.

2. Methodology

The experiment was conducted on a commercial piggery in NSW (Rivalea

Australia Pty Ltd., Corowa) during winter and spring. Over five weeks, 1216 Large

White x Landrace F1 sows (PrimeGro™ Genetics) ranging in age between parity 0

(pregnant gilts) and parity 6 prior to farrowing commenced the experiment when

they entered the farrowing shed in their 15th week of gestation. Sows were

allocated to either a treatment diet with no supplementary omega 3 fatty acids

from fish oil (Control) or a diet supplemented with 3 g/kg salmon oil (Omega 3).

Treatment diets were fed pre-farrowing, during lactation and between weaning to

mating. After weaning, 860 re-mated sows from the study group in lactation were

fed either an unsupplemented gestation diet or a diet supplemented with 6 g/kg

of fish oil in a 2 x 2 factorial design with lactation and gestation dietary treatment

as variables for the first 4 weeks of pregnancy. Thereafter all sows were fed a

standard diet during pregnancy. Subsequent pregnancy rates and litter size was

collected from farm records.

Animal management

The experiment was conducted according to Animal Ethics Committee approval

by the University of Adelaide (Project No. M-2009-147) and Rivalea Australia

Animal Ethics committee (Project No. 09R019C). Sows were sourced from a

commercial piggery at the Corowa site commencing in August. Each week

pregnant mixed-parity sows entered the farrowing sheds at 112 days of gestation.

On entry, sows were allocated to one of two lactation dietary treatments: either

Control or Omega 3 (3 g/kg fish oil), with one half of the shed allocated per

treatment per week. There were 608 sows that commenced the study as Controls

and 608 sows on the Omega 3 treatment at the start of lactation. To minimize

bias due to pen location within the shed, the treatment allocations on each half of

the shed were alternated between replicates. Data on previous litter size born

live and total born (including mummified foetuses and stillborns), and parity were

retrieved from farm records and current date of farrowing, litter size and pen

location were recorded. All sows were otherwise managed under commercial

practice, with litters being processed within 24 hours of birth; piglets injected

with 1 ml iron (Ferroject; Swift) and tails docked. Litter size was adjusted

according to rearing ability and ranged in number from 8 to 14. Some sows were

weaned early due to milking failure, sudden death or destruction due to injury. In

3

some cases, sows had an extended lactation if they were used as nursing sows to

maintain the litter. In these cases, the nursing sow was shifted to a pen and

continued on her respective treatment. Sows that had a shortened lactation (<10

days) due to milking failure or poor mothering ability, and nurse sows that had an

extended lactation (>32 days) were excluded from the analyzed data set. Sows

were weaned at 19.8±0.14 days (mean±SE) of lactation. Weaning occurred twice a

week. Of the total sows weaned, 398 sows on the Control treatment and 462 sows

on Omega 3 diets in lactation of the weaned sows were housed in individual stalls

in a study area of a commercial dry sow facility. Not all the sows commencing the

experimental diets in lactation were able to be retained for pregnancy treatment

allocation due to space limitations within the facility. There were more Omega 3

sows available to continue the experiment due to the commercial management of

the weaning, which was unintentional. The characteristics of the subset in terms

of litter size weaned, lactation length and parity were the same as the population

weaned. Within the rows of stalls filled following weaning each week, sows on

their respective lactation treatment were blocked together and continued to

receive their experimental lactation diet until mating.

Sows were mated at first oestrus detection by artificial insemination with

semen 3 x 109 sperm cells (Rivalea, Australia). Once mated, half the sows within

the weeks’ weaning block were allocated to a Control gestation diet and the other

half were allocated to an Omega 3 gestation diet with 6 g/kg fish oil. Sows were

remated the following day (+24 hours) and remained in the study area until

pregnancy was confirmed by ultrasound at 28 days. All sows ended their

experimental treatment diets at this point. Sows were then moved to an adjacent

dry sow shed and individually housed until entering the farrowing sheds on day 112

of gestation for the birth of their subsequent litter.

Diets and feeding

Diet composition of the Control and Omega 3 lactation diets and Control and

Omega 3 gestation diets are described in Table 1 with fatty acid profile described

in Table 2. Experimental lactation diets were formulated using wheat, cereals

and soybean and canola meals and provided 14.9 MJ DE/kg; 188 g crude

protein/kg; 0.51 g available lysine/MJ DE. Experimental gestation diets were

formulated using wheat and cereals and provided 12.9 MJ DE/kg; 144 g crude

protein/kg; 0.38 g available lysine/MJ DE. Other essential amino acids were

formulated as a ratio to lysine in all treatment diets. Omega 3 fatty acids were

supplied as fish oil in a liquid form containing antioxidants (Optigen Ingredients®,

Port Adelaide, Australia) and applied from a post-pellet spray applicator.

Supplementation with omega 3 fatty acids in the Omega 3 diets was achieved by

4

substituting tallow with fish oil. Other sources of unsaturated fatty acids were

kept to a minimum.

Following allocation and on the day of farrowing at the beginning of the

experiment, sows were fed 3 kg of their lactation treatment diet each morning.

From the day after farrowing, sows were offered their treatment diet up to three

times a day based on appetite. All sows were weaned from their litters and

relocated to individual gestation housing. Sows continued to be fed their

lactation diet after weaning once a day at 2.7 kg until oestrus and mating (pre-

mating period). After first service, mated sows were fed 2.5 kg of their treatment

gestation diet once a day for 28 days (early pregnancy period). For the remainder

of pregnancy, all sows were offered a commercial gestation diet fed once a day at

2.7 kg until transfer to the farrowing shed for their subsequent litter. The

commercial gestation diet used after four weeks of pregnancy was based on wheat

and cereals and contained no fish oil.

Treatment diets were analysed for fatty acids at the Nutrition and Functional

Foods Laboratory, The University of Adelaide, Waite Campus, South Australia.

Statistical analysis

Data was processed through a General Linear Model (GLM) analysis of variance

for treatments in a randomized design model assuming equal variance (Sokal and

Rohlf, 1981). The analysis of variance was performed using SPSS v18.0 (SPSS Inc.,

1989-2009). In the analysis of subsequent litter size, only those sows that

remained in the study area of the dry sow facility and were fed experimental

gestation diets were included. Any sow that returned to service and was re-mated

after the first post-weaning oestrus mating was included as a failed pregnancy in

the farrowing rate data analysis whilst the subsequent litter performance from

these returned and re-mated sows was excluded from further data analysis. The

subsequent litter data was normally distributed and was analysed by GLM

Univariate ANOVA with replicate and where stated parity were included as random

factors. Variables including lactation length, average lifetime litter size at the

start of the experiment included as covariates if significant in the model (P<0.10).

Comparisons between treatments were analyzed using Bonferroni adjustment to

confidence intervals for multiple comparison. The proportion of sows within the

study that were mated and farrowed (farrowing rate) were analyzed by Chi

square. All analyses were conducted at a confidence limit of 95%. Unless

otherwise stated, probability values >0.50 were described as not significant (NS)

5

3. Outcomes

Of the 1216 sows allocated to the study, 26 sows were taken off the study

during lactation due to (milking failure; 15 x Control, 11 Omega 3) and 42 for

extended lactations (nurse sows) (21 x Control, 21 x Omega 3). There were seven

sows removed due to mortality (3 x Control, 4 x Omega 3) during lactation. From

the production records, there was no evidence of any treatment effects on

lactation performance or sow mortality. The litter size weaned was unaffected by

dietary treatment and averaged 9.0±0.13. After weaning, there were six sows

removed due to sudden death or euthanasia (2 x Control, 4 x Omega 3). Omega 3

supplementation during lactation did not affect the proportion of sows weaned or

the resumption of oestrus and re-mated (Table 3). The interval to oestrus and re-

mating was similarly unaffected by Omega 3 supplementation during lactation and

post-weaning (7.0±0.2 days). The main reasons for failure to re-mate were due to

management decisions relating to physical issues (locomotion, udder, body

condition, infectious discharge: 13 x Control, 17 x Omega 3; χ2 0.51, P=0.477), or

mortality (sudden death & euthanasia: 2 x Control, 4 x Omega 3; χ2 0.65,

P=0.420). Out of all the sows weaned only three failed to resume oestrus after six

weeks (1 x Control, 2 x Omega 3, NS). Other reasons sows were removed after

weaning included culling for high stillbirths in the previous litter and for excessive

size.

Subsequent reproductive performance and litter size of the sows that remained

in the study area and continued their treatment diets for 28 days after mating is

summarized in Table 4. The subsequent farrowing rates were similar between

treatments (P=0.486). There were no significant differences in the cause of

mating failure between treatments; (return to oestrus=4.7%; pregnancy tested

negative=5.0%; death and euthanasia=4.1%; Late pregnancy failure (Not in Pig &

abortion) =2.3%; infectious discharge=1%).

Litter size born live was not significantly different between treatments (Table

4). Stillbirths tended to be higher in Omega 3 treatments that recorded higher

litter sizes. Subsequent litter size total born was significantly different between

treatments (P<0.05). Omega 3 sows fed supplemented diets from lactation

through to four weeks gestation (Omega 3/Omega 3) tended to have a higher total

litter size compared to the unsupplemented Controls (P=0.08). Subsequent total

born of sows fed Omega 3/Control and Control/Omega 3 were intermediate.

The average parity of the sows at weaning was 3.7±0.06 and was similarly

structured between treatments. Due to the small number of sows within each

parity, the data for subsequent litter size total born was analysed within parity

6

categories to reflect the subsequent litter size of weaned parity 1 sows, mid-

parity sows (parity 2 and 3 having their 3rd and 4th litter) and mature sows (parity

4-7 having their 5th-8th litter). There was no overall significant treatment x parity

interaction in subsequent litter size total born, however there was evidence of a

larger response in the mature sow parities allocated to Omega 3 when the dataset

was further separated into the parity categories defined above and analysed for

treatment response within each category. The subsequent litter size total born x

parity category is summarized in Table 5.

The subsequent litter size of parity 1 sows and parity 2-3 sows was unaffected

when fed with diets supplemented with fish oil during either lactation or early

pregnancy or both (Table 5). Subsequent sow farrowing rates for Control/Control,

Omega 3/Control, Control/Omega 3 and Omega 3/Omega 3 were also similar in

parity 1 (91.3%, 88.0%, 88.9%, 84.2%; NS) and parity 2-3 sows (82.2%, 88.0%,

77.9%, 87.9%; χ2 4.60, P=0.330).

In the mature parity category, there was a significant treatment response

(P<0.05) in subsequent litter size total born (Table 5). The increase in litter size

was greatest in the Omega 3 sows fed supplemented diets in lactation through to

four weeks gestation (Omega 3/Omega 3). Litter size of the Omega 3/Control

sows and Control/Omega 3 sows were intermediate but not significantly different

to the sows on Control/Control regimen. Figure 6.1 illustrates the pattern for

subsequent litter size total born as parity increases. In parity 4, 5 and 6,

subsequent litter size total born was significantly higher in Omega 3/Omega 3

sows compared to Control/Control and Omega 3/Control sows (P<0.05). Farrowing

rates were similar between Control/Control, Omega 3/Control, Control/Omega 3

and Omega 3/Omega 3 treatments in the mature parity category (82.1%, 82.4%,

77.9%, 81.5% respectively; NS).

7

Table 1.Composition and nutritive values of experimental diets (g/kg air-dry basis)

Ingredient Lactation Gestation Wheat

Control 563

Omega 3 563

Control 496

Omega 3 496

Barley 93 93 246 246 Millrun (wheat middlings) 73.7 73.7 190 190 Canola meal 60 60 - - Soybean meal 40 40 - - Meat meal 56.7 56.7 16.7 16.7 Blood meal 10 10 - - Molasses 10 10 - - Tallow 68 65 10 4 Water - - 10 10 Salt 3.5 3.5 3.0 3.0 Limestone 9.0 9.0 12.5 12.5 Dicalcium phosphorus - - 9.0 9.0 Potassium chloride 4.2 4.2 - - Monensin 1.0 1.0 1.0 1.0 Fish oil1 - 3.0 - 6.0 Synthetic lysine (L-lysine HCl) 1.36 1.36 1.53 1.53 Synthetic threonine 0.15 0.15 0.20 0.20 Mineral vitamin premix3 2.2 2.2 2.2 2.2 Phytase 1.0 1.0 1.0 1.0 Zinc bacitracin 2.5 2.5 - - Betaine 1.0 1.0 - - Mycotoxin binder 0.5 0.5 0.5 0.5 Antioxidant 0.2 0.2 - - Nutrient analyses2 Digestible energy (MJ/kg) 14.9 14.9 12.9 12.9 Crude protein 188 188 144 144 Crude fat 85 85 27 27 Crude fibre 36 36 42 42 Calcium 9.1 9.1 9.3 9.3 Total phosphorus 5.6 5.6 6.5 6.5 Available phosphorus 4.5 4.5 4.9 4.9 Lysine 9.0 9.0 6.0 6.0 Ileal digestible lysine (g/MJ DE) 0.51 0.51 0.38 0.38 Methionine 3.1 3.1 2.2 2.2 Methionine + cystine 6.4 6.3 5.0 5.0 Threonine 6.4 6.4 4.5 4.5 Valine 8.8 8.8 6.4 6.4 Isoleucine 6.2 6.2 4.5 4.5 Leucine 12.6 12.6 8.9 8.9 Histidine 4.6 4.6 3.2 3.2 Tryptophan 2.2 2.2 1.7 1.7 1Includes antioxidant added as a mixture of plant oil extracts at 3 g/kg. 2Nutrient value was based upon Rivalea Australia Pty Ltd proprietary composition data. aPremix provided the following nutrients (per kg air-dry diet): copper, 20 mg; iron, 80 mg; organic iron (Biolplex Iron®), 50 mg; manganese, 40 mg; zinc, 100 mg; iodine, 1 mg; selenium inorganic, 0.15 mg; organic selenium (Selplex®), 0.15; chromium picolinate, 3.2 mg, betaine, 100 mg; antioxidant (Endox®), 100 mg; vitamin A (retinol), 15 m.i.u.; vitamin D (cholecalciferol), 1.5 m.i.u.; vitamin E (α-tocopherol), 120 mg; vitamin B2 (riboflavin), 3.5 mg; vitamin B6 (pyridoxine), 2 mg; vitamin B12 (cyanocobalamin), 0.02 mg; biotin, 0.2 mg; folic acid, 0.5 mg; niacin, 20 mg; pantothenic acid, 5 mg.

8

Table 2. Fatty acid composition of treatment diets offered to sows during

lactation (g/100 g total fatty acids).

Lactation Gestation

Fatty acid (Common name) Control Omega 31 Control Omega 32

C16:0 (Palmitic acid) 23.1 22.8 20.8 19.2

C16:1 (Palmitoleic acid) 2.49 2.42 1.16 1.51

C18:0 (Stearic acid) 16.1 16.1 7.5 5.5

C18:1 (Oleic acid) 32.7 32.6 23.8 22.2

C18:2 n-6 (α-linoleic acid) 14.4 13.7 38.7 39.2

C18:3 n-6 (γ-linolenic acid) 0.03 0.03 0.01 0.03

C18:3 n-3 (α-linolenic) 1.60 1.59 2.89 3.18

C20:4 n-6 (arachidonic acid) 0.14 0.14 0.07 0.12

C20:5 n-3 (eicosapentaenoic acid) 0.03 0.20 0.02 0.72

C22:5 n-3 (docosapentaenoic acid) 0.11 0.17 0.05 0.30

C22:6 n-3 (docosahexaenoic acid) 0.04 0.22 0.04 0.79

Total n-6 14.7 14.1 39.0 39.6

Total n-3 1.90 2.30 3.05 5.08

n-6:n3 ratio 7.73 6.13 12.79 7.79

Total saturated 36.1 36.4 31.1 27.6

Total transaturated 36.1 3.02 31.1 0.90 1Fish oil included at 3 g/kg diet. 2Fish oil included at 6 g/kg diet.

Table 3. Post-weaning resumption of oestrus following supplementary feeding

during lactation and post-weaning with either unsupplemented lactation diet

(Control) or supplemented diet with 3 g/kg fish oil (Omega 3).

Lactation

No. sows

weaned/allocated

No. sows

re-mated/weaned

Wean-oestrus

(days)1

Control 565/608 544/565 6.8±0.28

Omega 3 571/608 546/571 7.2±0.28

χ2

P value

0.48

0.488

0.32

0.572

0.268

1 The estimated marginal mean values ±SE. Lactation length was included in model as covariate factor (19.8 days).

9

Table 4. Subsequent farrowing rates and litter size of re-mated sows fed either:

Control/Control, Omega 3/Control, Control/Omega 3 or Omega 3/Omega 3 diets

in lactation to pre-mating and/or during early pregnancy.

Lactation

to pre-

mating

Early

Pregnancy

Litters/mated

(Farrow rate)

Litter size

live born1

Still born &

mummified2

Litter size

total born3

Control Control 173/208

(83.2%)

10.6±0.27 1.10±0.14 11.7±0.27

Omega 3 Control 199/233

(85.4%)

10.8±0.25 1.17±0.13 12.0±0.25

Control

Omega 3

Omega 3

Omega 3

150/190

(78.9%)

193/229

(84.3%)

11.4±0.28

11.1±0.25

1.19±0.14

1.52±0.13

12.6±0.29

12.6±0.25

P value χ2 3.45,

P=0.486

0.234 0.100 0.041

Estimated marginal mean values (±SE). Parity included in GLM model as a random factor. Lactation length included in GLM model as a covariate (19.8 days) and 1lifetime average litter size born live born (11.4); 2lifetime average stillborn (0.81); 3lifetime average total born (12.3).

10

Table 5. Subsequent litter size total born within weaned parity 1, parity 2-3 and

mature sows (parity 4-7) sows fed diets as either: Control/Control, Omega

3/Control, Control/Omega 3 or Omega 3/Omega 3 diets in lactation to pre-mating

and/or during early pregnancy. Number of litters shown in brackets

Treatment Lact-pre-mating

Pregnancy

Control Control

Omega 3 Control

Control Omega 3

Omega 3 Omega 3

P value Parity 1

Live born

Total born

Parity 2-3

Live born

Total born

Parity 4-7

Live born

Total born

(21)

9.8±0.89

11.5±0.95

(74)

12.1±0.32

12.9±0.31

(78)

10.0±0.39

11.1±0.40a

(22)

11.5±0.66

12.4±0.70

(88)

11.4±0.30

12.5±0.29

(89)

10.3±0.37

11.7±0.38ab

(16)

12.1±0.85

12.6±0.90

(60)

11.6±0.38

12.8±0.36

(74)

11.1±0.41

12.4±0.42ab

(16)

11.2±0.82

11.6±0.87

(80)

11.7±0.31

12.8±0.30

(97)

10.7±0.06

12.8±0.37b

0.298

0.769

0.696

0.771

0.226

0.012

abcEstimated marginal mean values ±SE within column with different superscripts differ P<0.05. Lactation length and average lifetime litter size within each parity grouping included as a covariate.

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

CONT/CONT Omega 3/CONT CONT/Omega 3 Omega 3/Omega 3

Sub

sequ

ent l

itter

size

(tot

al b

orn)

Parity 1 Parity 2 Parity 3 Parity 4 Parity 5 Parity 6 Parity 7

Figure 1. Subsequent litter size total born x parity1 (mean±SE) when sows are fed

combinations of unsupplemented (Control) or fish oil supplemented diets (Omega

3) either during lactation and pre-mating and/or early pregnancy.1Parity at start

of the experiment during lactation.

11

DISCUSSION

Feeding sows with diets high in the long-chain omega 3 fatty acids EPA and DHA

during lactation, post-weaning and continuing through to four weeks of pregnancy

increased subsequent litter size in mature sows (parities 4-7). However, when

omega 3 supplemented diets were fed to parity 1 sows or mid parity sows (2-3)

during lactation, post-weaning and early pregnancy, there was no significant

difference in subsequent litter size compared to sows fed unsupplemented Control

diets. In the older parities, the response to omega 3 supplementation was largest

when supplementation continued after mating with 6 g/kg fish oil (15 g/day) fed

for 28 days post-mating. This response was significantly higher than the

unsupplemented Controls thereby supporting the second of our experimental

hypotheses in these parities. The response to omega 3 fatty acids on subsequent

litter size was more apparent when supplemented diets were fed in the early

pregnancy period.

In a previous study conducted at Rivalea (Smits et al, unpublished) we found

that subsequent total born increased when weaned sows (parity 1-6) were fed

omega 3 diets supplemented with 3 g/kg fish oil for 8 days prior to farrowing and

during lactation (19 days) when compared to sows fed unsupplemented Control

diets (10.7 vs. 9.8; P<0.05). After mating, all sows were fed an unsupplemented

gestation diet. In a further study, as part of the Pork CRC project 2F-102, we

reported that embryo survival and total embryo number at 23 days were increased

when mature parity sows (weaned parity 5-8) were fed omega-3 supplemented

diets with 3 g/kg fish oil during lactation and post-weaning up to re-mating (Smits

and Mitchell, 2009). In the literature, the response to polyunsaturated fatty acids

(PUFA’s) in pigs has been equivocal with some reporting positive responses on

litter size born (Palmer, et al., 1970, Spencer, et al., 2004, Webel, et al., 2004),

whereas other studies reported no significant increase in litter size born (Rooke,

et al., 2001), embryo number or embryo survival in either weaned mixed parity

sows (Perez-Rigau, et al., 1995) or gilts (Estienne, et al., 2006).

The fertility response to dietary supplementation may be through direct

nutritional effects (blastocyst growth and development) or indirect effects on

embryo survival (oocyte quality, progesterone and prostaglandin concentrations

(Ashworth and Antipatis, 1999, Ferguson, et al., 2006). In our experiment, the

response was clearly more evident in the oldest parities, rather than in weaned

parity 2-3 sows. Foxcroft (2006) and Vonnahme (2002) reported that embryo

survival declines with parity, whilst the number of ovulations either increases or

remains high. If embryo survival is already high, such as would be expected in the

mid-parity sows, then there may be small but insignificant responses to

supplementation. In weaned parity 1 sows, the response to omega 3 fatty acids

12

was not significant, although the small numbers within this parity group makes

conclusive interpretation of the data difficult. We found this in earlier studies

where gilts were fed supplemented diets prior to mating and produced positive

though statistically insignificant responses in litter size (Smits et al, unpublished,

Chapter 3, and Chapter 4). In the current experiment, although total litter size

born was significantly increased, subsequent live born was not. Other factors

limiting live born litter size at full term may become overriding, such as placental

efficiency or uterine capacity (Vonnahme, et al., 2002, Wilson, 2007). As total

litter size increased in our experiment, so too did the tendency for the number

still born to increase (P<0.100). The lack of a significant improvement in

subsequent litter size had born live highlights the limitations in improving

reproductive performance in old sows.

This experiment targeted nutritional supplementation at two critical stages of

the reproductive cycle: firstly where oocytes grow and mature during

folliculogenesis and secondly during the phase of early embryo growth,

development and implantation. Nutrition during lactation and before ovulation,

and then during early pregnancy are identified as contributing to successful

subsequent reproductive performance (Ashworth and Antipatis, 1999, Cosgrove, et

al., 1995, Ferguson, et al., 2006, Foxcroft, et al., 1994, Zak, et al., 1997).

Although there was a positive response when omega 3 fatty acids were fed to

older sows in lactation and pre-mating (i.e. pre-ovulation), the differences in

litter size were not statistically different.

Dietary supplementation with fish oil sources of EPA and DHA supplementation

increases the concentration of DHA in the developing embryo and DHA and EPA in

the endometrial tissue as early as day 19 of gestation (Brazle, et al., 2009). When

Omega 3 supplementation with fish oil has been shown to affect reproduction, it

has been through an increase in embryo survival whilst ovulation rate has been

unaffected (Webel, et al., 2004); Smits et al unpublished, Chapter 4; Smits et al

unpublished, Chapter 5). Little is understood as to the mechanism by which long-

chain PUFA’s, including EPA, DHA and the omega 6 fatty acid, arachidonic acid

(ARA), affects embryo survival. In dairy cattle, a number of authors report that

omega 3 fatty acids from vegetable sources and fish products can increase follicle

growth (Petit, et al., 2002, Robinson, et al., 2002, Thomas, et al., 1997) which

may improve oocyte quality and luteal functioning from the corpus luteum after

ovulation. In a separate experiment, we assessed in-vitro maturation responses in

embryos derived from oocytes recovered from sows either fed supplemented

omega 3 diets using fish oil in lactation and post-weaning or unsupplemented diets

(Mitchell et al, unpublished). In the omega 3 sows, we found that embryos were

more advanced in their development at day 6 compared to oocytes from

13

unsupplemented sows. Advancing the development of embryos, either due to

oocyte quality or due to direct effects on embryo uptake of EPA and DHA before

implantation could increase oestrogen production and luteal support of the

conceptus.

The mode of action for omega 3 fatty acids in sows fed supplemented diets

post-mating is even less understood. Progesterone is synthesized from cholesterol

and regulated by prostaglandins (Ojeda, et al., 1981), and so fatty acids of either

omega 3 or omega 6 can be substrates for progesterone synthesis. Armstrong et

al (2006) demonstrated that LH receptor expression is increased and was

associated with increased progesterone synthesis from granulosa cells cultured

with omega 6-derived prostaglandin, PGE2. Low levels of progesterone pre and

peri-implantation have been implicated in low embryo survival in gilts and sows

(Ashworth, 1991, Jindal, et al., 1997, Pharazyn, et al., 1991). In a diet where

total fat content is similar to the unsupplemented control, as in our experiment,

an effect on progesterone would only be possible if there is some change on the

regulation of progesterone synthesis due to the fatty acid profile. In cattle, Burke

et al (1997) found that there was a higher proportion of cows with an elevated

progesterone pattern 48 hours after oestrus induction when fed diets

supplemented with fish meal. However, others have reported a lack of effect of

PUFA’s from fish byproducts on progesterone (Mattos, et al., 2002, Trujillo and

Broughton, 1995). We propose that combining pre- and post-mating

supplementation with omega 3 fatty acids from fish oil improved oocyte quality,

leading to enhanced blastocyst development, and further supported by increased

luteal function from the ovary which increased embryo survival and subsequent

reproductive performance.

Low reproductive performance has been recognized as a major contributor to

high sow culling rates and early exit from the breeding herd. Hughes and Varley

(2003) illustrated from commercial farm records, and where this current

experiment was conducted, that sow litter size declines after parity 4.The latter

is obvious from the litter size results for the control sows reported in Figure 1. In

the past, sow fecundity remained high beyond parity 4 or 5, such that cull for age

management decisions which were based on declining litter size and increased still

births were not introduced until parity 7 or older. Increasing the fertility of

multiparous sows and maintaining maximum fertility levels for longer increases

sow longevity and lifetime performance, and consequently profitability from the

breeding herd (Dhuyvetter, 2000, Dijkhuizen, et al., 1989, Levis, 2005).

Depending on costs, the industry regards that culling sows before parity 3 is below

the financial break-even return for gilt replacements (Levis, 2005). Therefore,

14

this outcome could provide a commercial solution for producers to keep sows at a

high level of productivity for longer.

4. Application of Research

The use of a nutritional approach to improve fertility of multiparous sows is

easy to adopt and offers a strategy that would keep older sows in the herd for

longer. A decision by APVMA two years ago to minimize the disease risk associated

with imported raw fish oil being used in feed manufacturing plants has resulted in

an increase in ingredient cost due to further processing. The cost of commercially

available semi-refined fish oil ranges from $3.65 to $6/kg. At the low inclusion

rates used in this experiment, the cost is small. Ordering and feeding a separate

diet in early pregnancy may be limiting in some farms, however, it would be

suitable for those that move sows from stalls to groups at 4-6 weeks, or batch-

farrow operations. These inclusion levels are well below the levels that could

cause off-flavours in sow meat (Irie and Sakimoto, 1992, Leskanich, et al., 1997,

Melton, 1990).

5. Conclusion

Feeding weaned sows with diets supplemented with fish oil during lactation,

post-weaning and early pregnancy significantly increased subsequent litter size,

with a larger response observed in older parity sows than mid-parity sows. There

was evidence of an effect of treatment feeding regimen on reproductive outcome

such that continuing to feed an omega-3 supplemented diet in early pregnancy

maximized the response. Dietary supplementation of sow diets in lactation and

early pregnancy offers producers a nutritional strategy that could overcome

declining productivity in sows increasing in age.

6. Limitations/Risks

In sow herd populations where embryo survival is not limiting fertility, the

response to supplemental omega 3 through fish oil may be less than reported

here. We know from the previous project 2F-102 that supplementation in gilts

does not significantly increase first-litter size. We also didn’t find any increase in

second litter size when parity 1 sows were fed supplemented diets in lactation,

post-weaning and gestation when weaned sows were held over to 2nd post-weaning

15

oestrus (skip-a-heat mated). Strategic use of supplemented diets or top dressing

is recommended.

The use of vegetable sources of omega 3 fatty acids supplying α-linolenic acid is

not a recommended substitute for fish oil due to low bioconversion to long-chain

EPA and DHA.

7. Recommendations

As a result of the outcomes in this study the following recommendations have

been made:

1. Supplementation with low levels of fish oil (<1% dietary inclusion) can

improve sow fertility and litter size of maturing parities.

2. Feeding supplemented diets in lactation and post-weaning through to early

pregnancy (post-implantation) at 18 g fish oil/day in lactation and 15 g fish

oil/day in gestation increased the responsiveness to long-chain omega 3

fatty acids EPA and DHA.

3. Semi-refined fish oil products are commercially available to producers and

offer producers a nutritional strategy to overcome declining productivity in

sows increasing in age.

16

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Appendix 1 - Notes

Confidential Information

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Appendices

Appendix 1: